Latina women are underrepresented in Science, Technology, Engineering, Math (STEM) education majors and careers (NCES, 2019); Thus, broadening representation of Latinas in STEM is critical to diversify the workforce and to promote innovation and advancement. Past work with Latina college students has shown that contextual experiences (i.e., college, family) contribute to their STEM beliefs and subsequent STEM degree continuation (Flores, 2011). Familial relationships, in particular, have been noted as salient contributors to Latinas' sense of self and STEM identity (Rodriguez et al., 2019). To advance the field, however, we must understand how earlier experiences and familial mechanisms shape Latina adolescents' ethnic-racial identity, STEM self-perceptions, and persistence. This dissertation incorporates Spencer's (1995) Phenomenological Variant of Ecological Systems theory (PVEST) and Velez-Ibanez's and Greenberg's (1992) Funds of Knowledge (FoK) theory into a broader conceptualization of ethnic-racial identity, science and math self-efficacy, and the odds of majoring in STEM among Latina adolescents. Through two interrelated papers, this dissertation informs our interpretation of identity development (i.e., ethnicity/race; science and math self-efficacy) and the likelihood of pursuing a STEM major from early adolescence into young adulthood. The first paper provides a better understanding of how parental cultural socialization shapes Latina adolescents' (n=195) science and math grades through the interconnection of their ethnic-racial identity. Using longitudinal data from the High School Longitudinal Study 2009, the second paper examines how parental STEM engagement contributes to a nationally representative sample of Latina adolescents' (n=1,927) science and math self-efficacy and likelihood of majoring in STEM over time. Collectively, this two-study dissertation uncovers the role of familial processes on Latina adolescents' STEM achievement outcomes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]